“The children are tough and very well organised,” said one member of staff. “They stop at nothing to get what they want, and work in gangs.

“We can only do so much, but arrests are usually impossible because of their young age. If they are kicked out, they return the next day. They are very aggressive towards staff, putting people in danger of attack.”

About 100 staff gathered in front of the Ministry of Culture following the walk-out to demand action.

Two years ago, France’s then Interior Minister said that the vast majority of street robberies in Paris were being carried out by the children of Romanian immigrants.

Claude Gueant said the eastern European state was responsible for exporting some of the most notorious sneak thieves in the world.

Many operated in gangs around the Gare du Nord Eurostar station, preying on British travellers as they arrived from London.

Romania joined the EU in 2007 but faced restrictions on immigration which are set to be lifted next year, leading to an expected influx into countries like Britain.

The Louvre normally attracts up to 30,000 visitors a day at this time of year. More than eight million people a year visit the Louvre, which is full of artistic treasures including the Mona Lisa.